1. Field of the Invention
This invention relates to a feedthrough of an optical submerged repeater used in a long-distance, optical-fiber submarine cable system in the field of optical communication employing a low-loss optical fiber.
2. Description of the Prior Art
An optical submerged repeater is laid in the sea at a depth of several thousand meters and exposed to a water pressure of several hundred atmospheric pressures; therefore, optical and electronic circuits of the optical submerged repeater are housed in a pressure resisting container made of a material of high durability against seawater, for example, stainless steel or beryllium copper. The optical and electronic circuits in the pressure resisting container and an optical-fiber submarine cable are interconnected via a feedthrough attached to an end face plate of the pressure resisting container to serve as an introducing part for an optical fiber and a power feeding conductor. The pressure in the pressure resisting container is usually 0 to 1 atmospheric pressures in terms of gauge pressure and a pressure difference between the inside and outside of the pressure resisting container is very large. Accordingly, the feedthrough is required to have a construction which withstands a high pressure while retaining a high degree of airtightness.